Primary zone for gas turbine combustor



April4 8, 1958 w. L. cHRls'rENsEN PRIMARY ZONE FOR GAS TURBINE COMBUSTORFiled Oct. 25. 1956 M/ Nm..

the primary zone.

United States Patent O "ce PRIMARY ZQNE FR GAS TURBINE CMBUSTOR WillardL. Christensen, Newtown, Conn., assigner, by mesne assignments, to theUnited States of America as represented by the Secretary of the NavyApplication cto'ber 23, 1956, Serial No. 617,895

2 Claims. (Cl. 6039.71)

This invention relates to a primary burning zone for a gas turbinecombustor.

ln gas turbine engines, jet combustion is accomplished by the`continuous burning of fuel in a confined space to obtain power directlyfrom the hot products of cornbustion. in such engines a high velocityair stream is forced by a compressor into the combustion chamber wherefuel is m'med with the compressor air. Combustion occurs primarily inthe flame zone and this provides the Working medium for the turbine.

The optimum performance of a compressonburnerturbine type engine is toobtain the highest stable heat release in the combustion chamber. Thishigh efficiency should be for a wide range of fuel' rates and air flowconditions. Since there are few variables in a given engine design, abasic method of obtaining increased efciency is to pre-treat the fuel tostabilize the flame. The performance is greatly increased if a catalyticagent can be employed in the primary zone to provide a Stabi* lizedregion of burning.

The present invention pre-treats the fuel by a heated target whichutilizes the heat from the burning gases in The incoming fuel isdirected at high velocity onto the target where it is heated tovaporization and combines with hot gases. This mixture is then unitedwith the primary air from the compressor and introduced into thecombustion chamber. To assist in complete burning in the unit the targetmay be coated with a catalytic agent.. Thus, burning efficiency isincreased and stabilized enabling a great reduction in length andweight.

lt is an object of this invention to provide a gas turbine combustorwherein the income fuel is pre-treated by a heated target.

lt is a further object of this invention to provide a gas turbinecombustor wherein the injected fuel is vaporized by heat derived fromthe primary burning section.

Other objects and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawing, the single figure of whichshows a cutaway longitudinal section through a gas turbine combustorembodying the invention. p

Referring more particularly to the drawing, the preferred embodiment ofthe invention includes a gas turbine combustor having an outer casing 1.Mounted within and spaced from the outer casing l is an open endedcylindrical casing 2 having a plurality of openings 3 through which thenecessary secondary or cooling air may enter. Casing 2 is rigidlyconnected to casing 1 by a plurality of struts extending between thecasings, two of the struts 38 and 40 being shown and being secured tothe casings by any suitable means such as welding.

A circular bale 4 is` located in the forward end of the cylindricalcasing 2. A fitting 5 on the `baille 4 receives the fuel line 6 so thatfuel may be ejected through the baflle. Spaced from the rearward side ofthe baille 4 2,829,494 Patented Apr. 8, 1958 there is a circular ceramictarget 7 having a downstream face 8 and an upstream face 10. The target7 is po sitioned parallel to but spaced from the baie 4 so that fuelejected from the fitting 5 will impinge on the target. The downstreamface 3 of the target is exposed to the primary combustion zone 9. Thehot gases in the com* bustion zone 9 heat the ceramic target`7 so thatthe fuel directed on the target 7 by the fitting 5 is vaporized. Boththe downstream face 8 and the upstream face 10 of the target 7 arecoatedwith a catalytic agent. As a general rule, catalytic agents arenot effective on a surface that is wetted by fuel. Howeven since theupstream `face 1lb of the target 7 in the preferred embodiment of theinvention is at a sufliciently high temperature, the upstream face 10will be in a gaseous area and a catalytic agent would thus be effective.

A fuel mixing chamber l1 is located between the baie 4 and the target 7.This chamber is partially enclosed by a tapering circular shield 12. Thefront end 13 of the shield 12 is parallel to but spaced from the curvedlip portion 14 of the baille 4 providing an annular opening 15 throughwhich the fuel mixture may pass. The other end 16 of the shield 12 isconcentric to but spaced from the target 7 to 'form a ring shapedopening 17 through which some of the hot gases from the primarycombustion zone 9 may pass. The baffle 4, the target 7 and the shield i2are secured together to form one unit and the unit is mounted in theforward end of the casing 2. Batlle 4 and shield 12 are rigidlyconnected by a plurality of strut members 24, 26 and 28 and target 7 isconnected to the end 16 of shield 12 by a plurality of pins 30 (only twoshown). The unit assembly of baiile 4, target 7 and shield 12 is in turnrigidly attached to cylindrical casing 2 by strut members 32, 34 and 36which extend between casing 2 and shield 12 and which may be securedthereto by any suitable means such as welding.

The primary air is introduced through an annular venturi 18 surroundingthe fuel chamber. The venturi 13 is formed by a ring shaped member 19having a curved side wall 20 concentric with and spaced from the curvedlip portion 14. The side wall 20 extends rearwardly past the end 13 ofthe section 12. The member 19 is mounted on the casing 2 to provide anannular opening 21. Member 19 is connected to casing 2 in this preferredembodiment by a plurality of rods 42 (only two shown) which extendbetween the member 19 and` casing 2 and which are secured thereto by anysuitable means such as by welding (not shown). It will be appreciated,however, that any suitable type of connecting means other than rods 42may be used.

In operation of the target 7 is heated to a high temperature by the hetgases in the primary combustion chamber. Fuel is injected into the fuelmixing chamber 11 and is vaporized by the heated target. The vaporizedfuel then mixes with the hot gases entering the fuel mixing chamberthrough the circular opening 17. As the primary air passes through theannular venturi 1S surrounding the `fuel mixing chamber, it draws thefuel-hot gas mixture out of the chamber and into the high velocityprimary air stream. The turbulence caused by the expansion at locations22 thoroughly mixes the combustionable elements so that they may beignited and burned in the primarycharnber.

This type of gas turbine combustor primary zone is applicable to eithera can or an annular type burner where a series of these chambers wouldbe arranged on the upstream face.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. A primary zone for a gas turbine combustor comprising an outercasing, an inner cylinder mounted in said casing and open at both ends,a fuel supply means mounted in said casing in the center thereof andadjacent one end of said cylinder, an annular venturi surrounding saidfuel supply means through which primary air oWs, an annular shieldmounted in said cylinder spaced from said venturi and forming a fuel andair mixing chamber, a ceramic target mounted in said mixing chamber andbeing of a lesser diameter than the inner diameter of the chamberwhereby hot gases from the rest of the cylinder which forms a primarycombustion zone will pass between said target and said shield andvaporize the incoming fuel and the primary air passing through theventuri will draw the mixture thus formed into the primary combustionzone.

2. A primary zone for a gas turbine combustor as in claim 1 wherein theceramic target is coated with a catalytic agent.

References Cited in the file of this patent UNITED STATES PATENTS1,052,588 Janicki Feb. 11, 1913 2,385,833 Nahigyan Oct. 2, 19452,433,943 Zwicky et al Ian. 6, 1948 2,554,401 Christensen et a1 May 22,1951 FOREIGN PATENTS 201,112 Australia Feb. 6, 1956

